The field of the invention relates generally to turbine buckets and, more particularly, to a turbine bucket that includes a cooling circuit with cooling holes sized and positioned to facilitate optimizing cooling ability and turbine efficiency.
In known gas turbine engines, combustion gases cause rotation of a turbine which drives a compressor. The compressor supplies pressurized air to a combustor which generates the combustion gases. Because such engines operate at relatively high temperatures, the capacity of such an engine may be limited by the materials used in fabricating the turbine blades, sometimes referred to herein as “buckets.” More specifically, higher temperatures may cause thermal stresses to develop within the blades which may limit their operation. Such stresses may be more severe in industrial gas turbine engines because of the relatively large size of the turbine blades.
Turbines are designed to operate at a predetermined temperature that facilitates a desired performance and efficiency. Typically, newer turbines are designed to operate at higher temperatures, which necessitates greater cooling of the blades than blades used in turbines operating at lower temperatures. After continued exposure to high temperatures, turbine blades may require replacement.
To enable the turbines to operate with higher operating temperatures and increased engine efficiency without risking blade failure, at least some turbines use hollow, convectively-cooled turbine blades. At least some of such blades include interior cooling passageways which provide cooling flow to the interior of the blades to facilitate maintaining the blade at a relatively uniform temperature. Turbine air flow is diverted from a compressor into the interior passageways within the blades. When turbine blades are replaced, it may be desirable to maintain a substantially similar level of cooling flow as was previously present.